Apparatus for lapping or grinding



May 8, 1934.

H. J. WILLS APPARATUS FOR LAPPING OR GRINDING Filed Dec. 25, 1951 2 Sheets-Sheet 1 INVENTOR HERBERT .1. wn.\.s.

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APPARATUS FOR LAPPING 0R GRINDING Filed Dec. 26, 1931 2 Sheets-Sheet 2 x Z2 Z5 18 1.9 i-

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APPARATUS FOR LAPPING R GRINDING Application December 26, 1931, Serial No. 583,313

6 Claims. (Cl. 51-156) resists NT GFFlC My invention relates to an improved process of lapping or grinding spherical or cylindrical parts and to apparatus for carrying out my improved process.

In my U. S. Patent No. 1,784,648, dated December 9, 1930, (reissued November l, 1933, as Reissue Patent No. 19003) I have described apparatus for the automatic lapping or grinding of short cylindrical parts. The present application l9 discloses apparatus for lapping or grinding spherical parts or cylindrical parts, which cylindrical parts may be of unlimited length.

In the ordinary process of grinding cylindrical parts the work piece is mounted between the head stock and tail stock of a lathe mechanism. The work piece is rotated while it is subjected to the grinding action of an abrasive wheel which rotates about an axis parallel to the axis of rotation of the work piece. The grinding wheel is displaced in a direction parallel to its axis while it is in rapid rotation. This method of grinding a cylindrical part requires the most painstaking care on the part of the operator. An excessive amount of time is required for finishing each piece of work.

The Well known process of centerless grinding is an improvement on the ordinary process of cylindrical grinding from the point of View of the time and attention required. The principal elements of a centerless grinding machine are the grinding wheel, the regulating or feed wheel, and the work rest. In this apparatus the grinding is done along a line contact between the grinding wheel and the work piece. From some points of view it is desirable to have a greater area of grinding contact than is afforded by the centerless grinding machines. My improved process of grinding makes use of much larger areas of grinding or lapping contact than are used in centerless grinding machines.

Examples of mechanism used in carrying out my invention are illustrated in the accompanying drawings in which:

Figure 1 is a plan View of apparatus for lapping or grinding a plurality of spherical parts in a continuous process by means of which a very large number of said parts are under treatment at one time;

Figure 1A indicates a transverse section 0 lapping or grinding bar shown in Fig. 1;

Figure 2 is a section on the line IIII of Fig. 1; v

Figure 3 is a vi w similar to Fig. 2 of a modified form of apparatus suitable for lapping or grinding cylindrical parts of limited length;

Figure 4 is an elevation of a form of apparatus adapted for lapping or grinding long or short cylindrical parts;

Figure 5 is a section on the line VV of Figure 4;

Figure 6 illustrates a modification of the apparatus indicated in Figures 4 and 5, which modified apparatus is particularly adapted for treatment of short cylindrical parts;

Figure 7 is a plan view of apparatus having a plurality of cooperating lapping bars, the upper plate being partly broken away;

Figure 8 is a section on the line VIIIVIII of Fig. 7;

Figure 9 is a plan view of apparatus in whioh an adjustable wedging device is used for varying the rate of grinding or lapping of a cylindrical or spherical part;

Figure 10 shows in elevation the modification illustrated in Fig. 9; and

Figure 11 is a detail elevation illustrating a method of adjustably rotating the lapping bar shown in Figure 10.

Referring to the drawings in more detail the apparatus illustrated by Figures 1 and 2 comprises a driving plate 1 which is provided with a spiral groove 3 extending from the inlet 4 on the circumference to a central opening 5.

A plurality of grooved lapping bars 6 are placed a above the driving plate in such positions that spherical parts 7 are rotated against the grooved surface 16 of the lapping bar when the driving plate is rotated in the direction of the arrow A. The spherical parts to be worked are fed into the groove on the driving plate at 4. After they have travelled the length of the spiral groove they are dropped through the central opening 5 and pass through a runway in the driving shaft 8 to a trough 11 and thence to a suitable receptacle.

The bars 6 are composed of bonded abrasive when it is desired that they exert a grinding action on the spherical parts. These grinding bars have a transverse section similar to that shown in Fig. 1A. When only a lapping or polishing action is desired the bars 6 are made of soft material such as wood or brass, and powdered abrasive is red to the grooved surface of the lapping bar. In Fig. 2 some of the fine abrasive is caught in this soft grooved surface or" the lapping bar and protects the soft material to a large extent from abrasion while the spherical parts are being lapped. The groove 3 has a transverse radius of curvature approximately equal to the radius of a spherical part under treatment. In Fig. 2 there is indicated a funnel 31 (of which there may be several) from which finely divided abrasive drops on the surface of the driving member 1. The rotation of the member 1 brings the fine abrasive into contact with the balls 7 and grooved surface of the lapping bar 6.

The motion of a spherical part under treatment has a component along the grooved bar toward the central opening of the driving plate. This movement along the grooved surface of the bar is accompanied by a radially inward force exerted on the ball by the outer surface of the groove in the plate. While the principal force exerted by the plate on the ball is in the direction of the groove and tends to roll the ball about an axis perpendicular .to the groove, the component force referred to just above tends to roll the ball about an axis parallel to the groove. The effect of the component force is therefore to increase the uniformity of the lapping or grinding action exerted on the ball.

In the modification shown in Fig. 3 the transverse section of the groove is shown as rectangular. This form of the apparatus is intended for the lapping of short cylindrical parts which are placed in the grooves with their principal axes parallel to the lapping or grinding bar. As in the operation described for the lapping or grinding of spherical parts the cylindrical parts are subjected to a rolling action in contact with a lapping bar 6. The cylindrical parts are also subjected to a simultaneous sliding action along the bar. The greath length of the spiral path effects an extended lapping or grinding action on the cylindrical part under treatment.

In the mechanism shown in Figures 4 and 5 the work 2 is rotated by means of a plate 12 and a roller 13 which have a relative rotation. Either of the members 12 or 13 may be made the driving member while the other member is loosely mounted or is rotated with a smaller peripheral speed (measured at the line of contact with the work piece) than the other member. The work piece 2 is forced by the relative movement of the members 12 and 13 into contact with a grooved surface 15 on a lapping or grinding bar 14. This grooved surface forms part of a cylindrical surface whose principal axis is parallel to the arrow B shown in Fig. 4. The direction indicated by B is therefore also parallel to the principal axis of the cylinder 2. The cylinder 2 contacts with the frustoconical surface of the plate 12 along a line which is parallel to the arrow B but which does not intersect the axis of rotation of the plate 12. The offset of the axial direction for the member 2 with respect to the axis of 12 is such that the rotations of the members 12 and 13 not only rotate 2 with respect to the grooved surface 15 of the bar 14, but also slide or translate 2 along the groove in the direction B or in the opposite direction.

The apparatus shown in Figures 4 and 5 is particularly adapted for grinding or lapping cylindrical parts of unlimited length. The cylinder 2 is supported by means of rollers (not shown) to permit the rotation and translation of 2 with respect to the grooved surface of the stationary bar 14.

The apparatus shown in Fig. 6 is analogous in its action to that shown in Fig. 4 except that it is only adapted for the lapping or grinding of short cylindrical parts. The short cylinder 2' is rotated against a grooved surface in the bar 14. The axis of the cylinder 2 does not intersect the axis of rotation of 12 but is so offset that the piece 2' is fed toward or away from the central opening of the plate 12.

The apparatus shown in Figures '7 and 8 has a supporting plate 17 in which there is no central opening. A short cylindrical part 22 is rotated (by means of a relative rotation of the lower plate 17 and an upper plate 18) first against the grooved surface of a lapping or grinding bar 19 and then against a similar bar 21. The respective inclinations of the bars 19 and 21 with respect to the adjacent radii of the plates 1'7 and 18 are such that when the plate 17 is the driving plate and is rotated in the direction of the arrow C, the cylindrical part 22 is rotated against 19 and at the same time translated inwardly along the grooved surface of 19. In the course of time the piece 22 partially clears itself from the bar 19 and passes under the plate-shaped hollow 23 in the upper plate 18. The piece 22 is subjected to a turning moment which in time carries it around into contact with the lapping bar 21. The inclination of the bar 21 is such that the cylinder 2 is moved outwardly along the bar 21 and finally reaches the circumference of the plate 17 where it falls out into a suitable receptacle such as a trough one of whose surfaces may be inclined outwardly and downwardly from the plate 17 to remove the finished pieces without injury.

In the modification shown in Figures 9 and 10 a driving plate 25 rotates and translates the work piece 26 in contact with an adjustable lapping bar 27 as shown in Fig. 9. By turning the bar 27 about a longitudinal axis in the direction of the arrow shown in Fig. 9 (or in the reverse direc tion) the pressure or frictional force exerted on the work piece can be varied in magnitude and direction. The action in this case may be otherwise expressed by stating that the rotatable bar 27 exerts a wedging action on the work piece 26, the amount of the wedging action varying with the angular position of the bar 27. As shown in Fig. 11 the lapping bar 27 is rotatable about a rod 28 and can be held in any desired angular position by means of a set screw 29. Means for attaching the rotatable lapping bar and its supporting rod to a base are indicated at 30.

In all the modifications of my apparatus the grinding or lapping bar has a longitudinal groove against which the spherical or cylindrical part is rotated and translated. The rate of sliding or translating movement of the work piece with respect to the bar is a principal factor in determining the duration of the lapping or grinding process.

While lapping and grinding processes are closely related and merge into each other, the principal distinction between the two processes lies in the fact that in the grinding process the abrasive matter is composed of grains which are relatively fixed in position with respect to each other as in a bonded abrasive bar. In the lapping process on the other hand the abrasion is performed by relatively movable fine abrasive particles which are supplied in powdered form. In the lapping process the lapping bar is made of soft material such as wood, brass or cast iron.

Where the finished parts reach a central opening a runway is provided (as indicated in Fig. 2) through which the finished parts pass to a trough 11 outside the driving shaft. In the case of the modifications shown in Figures 4 and 5, there are no central openings in the driving plate. Travelling conveyors (not shown) can be placed so as to receive the work piece when it passes out of contact with the lapping or grinding bar.

My various forms of apparatus are particularly adapted for automatic grinding or lapping with a minimum of attention on the part of the operator.

I claim:

1. Apparatus for the continuous lapping of a spherical or cylindrical part comprising a driving plate, a spiral groove in said driving plate for guiding said part under treatment, a grooved lapping bar adjacent said spirally grooved plate against which the part under treatment is rotated and translated, and means for supplying finely divided abrasive to the lapping surface.

2. Apparatus for the continuous grinding of a spherical or cylindrical part comprising a driving plate, a spiral groove in said driving plate for guiding said part under treatment, and a grooved abrasive bar adjacent said spirally grooved plate against which the part under treatment is rotated and translated.

3. Apparatus for grinding or lapping a cylindrical part of unlimited length comprising a retatable plate having a frustoconical supporting surface, a fixed grooved lapping bar adjacent said supporting surface, a rotatable traction roller adjacent said lapping bar, the rotatable and fixed parts being so positioned that relative rotation of the two rotatable parts rotates and translates the cylindrical part against the grooved lapping sur face, and means for supplying abrasive to the lapping surface.

4. Apparatus for the grinding of short cylindrical parts comprising a rotatable plate having a central opening, a fixed bar of abrasive material adjacent to said plate and having a straight groove extended at an angle to the adjacent radius of the plate, whereby rotation of the plate will turn a part to be ground in contact with the grooved surface of the bar and simultaneously slide the part along the groove, and a traction roller positioned to retain the said part in contact with the groove and to cooperate with the plate in turning and sliding the part to be ground.

5. Apparatus for the lapping of short cylindrical parts comprising a rotatable plate having a central opening, a fixed bar of soft material adjacent to said plate and having a straight groove extending at an angle to the adjacent radius of the plate whereby rotation of the plate will turn a part to be lapped in contact with the grooved surface of the bar and simultaneously slide the part along the groove, a traction roller positioned to retain the said part in contact with the groove and to cooperate with the plate in turning and sliding the part to be ground, and means for supplying fine abrasive at the lapping surface.

6. Apparatus for lapping cylindrical or spherical parts comprising a rotatable plate, and a lapping bar spaced from said rotatable plate surficiently to friotionally engage the part to be lapped along a grooved surface of the bar, the axis of the groove being inclined at an angle to the adjacent radius of the plate whereby the rotation of the plate slides the part to be lapped along the groove, the lapping bar being also rotatably adjustable about an axis parallel to the axis of the groove whereby an adjustable wedging action is exerted on the part being lapped.

HERBERT J. WILLS. 

